GB1044858A - A master cylinder for vehicular hydraulic braking systems - Google Patents

Abstract

1,044,858. Hydraulic brakes. KELSEY. HAYES CO. June 16, 1965 [June 18, 1964], No. 25535/65. Heading F2F. A master cylinder for an hydraulic brake system producing differential braking between the front and rear wheel brakes, comprises first and second pistons 32, 38 connected respectively to first and second sides of a piston 64 which is biased against the fluid pressure produced by the first piston 32 by means of a spring 74 and of which the first side is of greater effective area than the second side. The pistons 32, 38 are connected together and actuated by a rod 30 which is operated by a booster or by manual force. Fluid displaced by the first piston 32 passes through passages 48, 52 to the rear brake cylinders and also acts upwards on the lower side of the piston 64. Fluid displaced by the second piston 38 passes through passages 58, 60, 12 to the front brake cylinders and also acts downwards on the upper side of the piston 64, the effective area of this side being the annulus around a plunger 70 which extends from the piston through a seal 80 to be acted upon by the spring 74. Fluid from the chamber 36 containing the first piston 32 can pass through a passage 56 into the chamber 42 containing the second piston 38 until the passage is closed by movement of the pistons. As fluid is displaced to the brake cylinders the pressure in the chambers is initially equal, but when an hydraulic pressure about 300 p.s.i. is reached the piston 64 is raised against the action of the spring 74 causing fluid to be displaced to the front brake cylinders, and thereafter the pressure to the rear brake cylinders rises more slowly than the pressure supplied to the front brake cylinders. Passages in the pistons 64, 38 permit unidirectional flow from the chamber 36 to ensure that the pressure supplied to the front brake cylinders is never less than that supplied to the rear brakes.